Creating directories and files in /Library on os-x 10.8

Question

I want to install files to /Library/Python/2.7/site-packages on OS-X 10.8. I am logged in as Administrator, but I still get an error 'Permission denied'. Same error when I try to create a directory there from Terminal. I apparently don't have permission to write into the root area. How do I fix this?

Answer 1

Being logged in to MacOSX as "an administrator" grants you permission to execute certain privileged commands, but it does not make you root (user ID 0 - super user). The Python directory, and most everything under /Library, is owned and writable only by root: E.g.

mymac:Python kentalt$ ls -l
total 0
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.3
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.5
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.6
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.7
mymac:Python kentalt$ touch foo
touch: foo: Permission denied

Adminstrator can use sudo (execute a command as root user) with your admin passed:

mymac:Python kentalt$ sudo touch foo
Password:
mymac: Python kentalt$ ls -l
total 0
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.3
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.5
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.6
drwxr-xr-x  3 root  wheel  102 Jun 20  2012 2.7
-rw-r--r--  1 root  wheel    0 Jan 10 08:57 foo

Note that you have to use sudo with each such command (if you run several such commands in a short period of time it will not ask for your password each time):

mymac:Python kentalt$ rm foo
override rw-r--r--  root/wheel for foo? y
rm: foo: Permission denied
mymac:Python kentalt$ sudo rm foo
mymac:Python kentalt$ ls
2.3 2.5 2.6 2.7

You could also change directory permissions to allow group or everyone to write to it, rather than doing all maintenance as root -- beware that permission changes can break some programs or may get reverted on system updates, though Python is probably fine. Or add a symlink for site-packages to somewhere else in user-writable space, so you keep your updates clearly separate from system supported files.

You can use "sudo bash" to start a shell session as root. This is a really, really dangerous thing to do, because root can do pretty much anything, and may not even require a sanity check before removing your entire system, e.g., "rm -rf . /*" (a typo every old unix admin has done at least once).